Telemetering system



Patented Aug. 25, 1936 JNITED STES 'y attacca 'rnaanmrnmne srs'rnivi Herbert Dallmann, Berlin-Karlshorst, Germany,

assigner to General Electric Company, a corporation of New York .application .time 2t, isst, sei-iai no. '332,485

Germany JnlyllS, i933 s ois. (ci. iti-ssi) My invention relates to telemetering systems and concerns particularly systems in which a transmitted current is varied by means of a variable impedance in response to variations in a measurement or indication to be transmitted.

It is an object of my invention to provide a telemetering system in which only two conductors are required to connect transmitting and receiving stations and in which the accuracy is increased by eliminating movable contacts and the attendant variable contact resistance.

It is also an object of my invention to provide anarrangement which is independent of possible contact. In order to minimize the effect of the contact resistance, it becomes necessary to employ more than two conductors between the transmitting and receiving stations for the purpose of using some sort of ratio method.

The disadvantages of movable contacts may be overcome by utilizing a variable reactance or im-V pedance instead of a rheostat or potentiometer since a reactor may be constructed to have its impedance varied by moving the relative positions of the exciting Winding and an armature of the vane or coil type. In such reactors having relai tively movable members, however, the reaction between the members produces forces which tend to interfere with the setting of the position of the movable member by the movable pointer of the sending instrument and prevent 'obtaining a proper indication.

In accordance with my invention in its preferred form, I utilize a variable reactor orimpedance having a regulating arm mechanically connected to the -indicating pointer of an' instrument, the indications of which are to be transmitted, and I also utilize a force-producing element mechanically connected to the variable reactor to overcome the force produced by the reaction between the relatively movable members and having an exciting winding supplied by the same source of current as the excitingv winding of the variablexreactor. The parts are `so arranged that the force produced by the auxiliary torce-producing element varies in the same manner as the reaction between the elements of the variable reactor so that the reaction is balanced at all points.

The features of my invention whichI believe to be novel and patentable will be pointed out in the claims appended hereto. A better understanding oi myy invention, however, may be obtained by referring to the following description taken in connection with the accompanying drawing illustrating one embodiment of my invention in Fig. l, by means of a schematic diagram showing the electrical circuits, illustrating' another 4embodiment in Fig. 2 ,by a partial view and illustrating another embodiment of my invention in Fig. 3.

Referring more in detail to Fig. 1 of the drawing, a sender measuring or indicatingv instrument of any desired type is represented at il having a movable pointer l2, the indication of which is to be transmitted to a receiving station remote from the transmitting station at which the instrument it is located; A variable impedance i3 is provided having a regulating arm ill mechanically connected in any suitable manner as .instrument'employed ordinarily has a movement as great in size as the variable' impedance i i3 in order to insure ample torque for overcoming friction/ although, as explained hereinafter,l I provide a balanced arrangement in which, very little torque is required to be excited by the indicating instrument.

In the arrangement illustrated, the variable impedance I3 consists 'of a stationary exciting winding IG and a movable armature il comprising a sickle-shaped vane of iron or other magnetic material but it will be understood that ing I6. By virtue of the fact, however, that the reluctance'varies with variations in angular position of the vane I1, there is a force produced between winding I6 and the vane I1 acting in a counterclockwise direction, as shown by the arrow MI, tending to draw the vane I1 into the position of minimum reluctance.

In order to overcome this torque, I provide a torque or force-producing unit I8 having a movable member I9 mechanically connected to the movable member of reactor I3 in any desired manner as by means of shaft 20. The torqueproducing unit I8 may comprise any suitable device, preferably one having a torque or force which varies substantially in the samemanner as the force produced by the reaction between winding I6 and vane I1 of variableireactor I3. For example, .I may employ an induction disc motor having a rotor comprising a rotatable disc I9 cooperating with a stator comprising a stationary winding 2I on a shaded pole field structure carrying a shading coil 22 to produce a shifting magnetic field acting upon, the disc I9 to produce a torque M2 acting in a clockwise'direction to balance the 'torque MI produced in the variable reactor I3. Windings I6 and 2I are connected in series or parallel to a pair of conductors 23 and 24 leading to a source of alternating current 25 at the receiving station.

In the arrangement shown, in Fig. 1, the windings are connected in parallel and the torque produced in units I3 and I8 tends to vary in accordance with the square of the voltage of the supply source 25. However, it will be understood that, if desired, I may substitute units producing torques varying in a different manner with variations in voltage (or current in case of series connection) but, preferably, the relationship between torque and voltage (or current) is similar in both units in order that the torques will be balanced irrespective of voltage variations.

In the arrangement of Fig. 1, the rate of change of cross-sectional area of the vane I1 with respect to the angle through which the vane rotates is assumed to be such that a constant rate of change of reluctance with respect to the angle of deiiection is obtained with a result that the torque of the unit I3 is independent oi. the angular position of the movable member. Since the inductance disc motor unit I8 employs a uniform circular disc I9, its torque will also be independent of angular position. Ifl desired, however, torque balance for different angular positions may also be obtained without maintaining a. constant rate o1 change of reluctance with respect to angular deection in the unit I3. The torque produced by unit I8 may then be appropriately varied for different angular positions in any desired manner as by changing,r the composition, thickness.' or radius of the disc I9 in different portions of its periphery.

Fig. 2 illustrates such an arrangement in which the unit lI3 does not. have a constant rate of change of reluctance with respect to angular deilection and the induction disc I9' is made camshaped with a variable radius to compensate for variations in torque with respect to angular deflection of the unit I3.

Fig. 2 also illustrates an' arrangement in which the windings I 6 and 2I are connected in series so thatthe torques of the opposing units I3 and I8 vary substantially as the square of the current in the conductors 23 and 24.

At the receiving station, I provide a suitable .sented by showing the pointer and the plate 3| current-responsive receiver instrument 26, such as a crossed-coil ratio instrumentor impedance meter, for example, having cooperating crossed coils 21and 28. One of the coils 21, which may be referred to as the potential coil, is connected 5 across the source of current 25 and the other coil 28, which may be referred to as the current coil is connected in series with one of the conductors 24 joining the transmitting and receiving stations so that the instrument 26 measures the 10 ratio between ythe current and voltage supplied by the source 25 or the impedance of the load supplied by the source 25. The impedance obviously varies as the position of the regulating arm I4 of variable reactor I3' is varied in accordance with movements of the indicating arm I2 of instrument II. Consequently, the reading of the instrument 26 at the receiving station provides an indication of the reading of the instrument II at the transmitting station.

In the arrangement of Fig. 3, the variable impedance controlled by the movable element of the instrument II takes the form of an electrostatic or capacitative impedance or variable condenser 29. The variable condenser 29 has a pair of two 25 sets of relatively movable plates 3I and 32. In the arrangement shown, there is a stationary plate 32 and a relatively movafble plate 3I attached to the shaft 2U operated by the movable element, not shown, of the instrument II. The plates 3I and 32 are arranged to have a variable radius sov that, as the shaft 20 is rotated, the spacing between the plates 3I and 32 is varied to vary the capacity between them. This, of course, varies the impedance offered to the current supplied by the source 25. Electrostatic attraction tends to bring the plates 3| and 32 in the position in which they are closest together, producing a torque MI' which is balanced as in the arrangement of Fig. 1 by the torque M2 produced by an induction disk motor consisting of the induction disk I9 and iield coils 33 and 34. There is a condenser 35 in series with the coil 34 in order to produce a phase difference between the currents in the coils 33 and 34. The arrangement of Fig. 3 illustrates a modification of the arrangement shown in Fig. 1 for obtaining a shifting flux for producing rotation of the disk I9.

Preferably, in order to increase the admittance of the variable impedance 29 and thereby increase the relative eilect of deflection of the pointer I2, the current source 25' is provided, having greater than the usual commercial Irequency, and the measuring apparatus 28' adapted to such frequency is provided which may be calibrated directly in terms of the readings of the pointer I2.

The eiect on the spacing of the condenser plates of a deflection of the pointer I2 is repredotted in one scale position and in full lines in another scale position.

In accordance with the provisions ofthe patent statutes, I have described the principle o! operation of my invention together with the appa- 05 ratus which I now consider to represent the best embodiment thereof but I desire to have it un- {derstood that the apparatus shown and described and a movable armature mechanically connected to said pointer, and an induction motor unit hav- 4ing an exciting winding and an armature mechanically connected to the movable armature of said variable impedance and acting in opposition thereto, and a source of alternating current energizing said windings.

2. In a telemetric device of the variable impedance type, a variable mpedance having an exciting winding and an rmature.A one of which is movable with respect to the other, and an induction motor unit having a stator and a rotor,

one of which carries an exciting winding connected in parallel to the exciting winding oi said variable impedance, the rotor being mechanically connected to the movable member of said variable impedance and acting in opposition thereto,v

the arrangement being such that the i'orces produced by thereaction between the coacting elements in said variable impedance and by said induction motor unit vary at substantially the y same rate with voltage so that the forces remain balanced irrespective of variations in voltage applied to said exciting windings.

3. In a telemetric system, a source of current, a variable impedance supplied by said source and A4having relatively movable mutually reacting memberscadapted to have their relative position varied in response to variations in a measure ment to be transmitted to vary the impedance correspondingly, and a torce-producing movable element producing a force equal at any position to the force produced by the reaction between the relatively movable members of said variable impedance: said movable element being con-.

nected to oppose'said torce o! reaction.

4. In a telemetric system of the variable impedance type. a variable impedance having relatively movable mutually reacting membersV adapted to have their relative positions varied in response to variations in a measurement to bev transmitted to vary the impedance correspondingly, and means for balancing the' force of reaction between said relatively movable members substantially at any of their relative positions.

5. In a telemetric system of the variable impedan'ce type, a variable impedance having relatively movable mutually reacting members adapted to have their relative positions varied in response to variations in a measurement to be transmitted, means varying in force with the relative positions of said mutually reacting members at the same rate as the reaction for balancing the force of the mutual reactiony between said relatively movable members.

6. In a telemetric device of the-variable impedance type, a variable -inductive impedance having an exciting winding and a vane armature, one of which is movable with-respect to the other, the vane armature having a continuously variable cross section to provide variations in reluctance of the ilux path of said'exciting wind- 

